The 10 Gigabit per second (Gbps) data rate (e.g., 9.96 Gbps for SONET OC-192 and SDH STM-64, 10.3 Gbps for GbE LAN PHY, and 10.5 Gbps for 10 G Fiber Channel) is emerging as the most dominant interface rate between servers, routers, Ethernet switches, multi-service provisioning platforms (MSPPs), cross-connects, etc. in core, regional, metro, access, and enterprise networks. Pluggable transceivers configured to provide a 10 Gbps optical signal have been adopted by equipment vendors as an effective way to decouple design and development of the physical optical interface from the rest of the open systems interconnect (OSI) layer two and above functions on line cards (also known as blades) in servers, routers, Ethernet switches, MSPPs, cross-connects, etc.
Pluggable transceivers are defined through multi-source agreements (MSAs). MSAs are agreements for specifications of pluggable transceivers agreed to by two or more vendors and promulgated for other vendors and network operators to utilize. MSAs allow other vendors to design transceivers to the same specifications reducing risk for vendors and operators, increasing flexibility, and accelerating the introduction of new technology. Six such MSAs include XFP, XPAK, XENPAK, X2, XFP-E and SFP+. Additionally, new MSAs are emerging to address new services and advanced technology. Each MSA defines the transceiver's mechanical characteristics, management interfaces, electrical characteristics, optical characteristics, and thermal requirements. Because of MSA specifications, MSA-compliant pluggable transceivers are standardized among equipment vendors and network operators to support multiple sources for pluggable transceivers and interoperability. As such, MSA-compliant pluggable transceivers have become the dominant form of optical transmitters and receivers in the industry.
Advantageously, MSA-compliant pluggable transceivers ensure engineering re-use and compatibility between various applications and the physical media dependent transceivers. Further, equipment vendors realize streamlined manufacturing and inventory control by removing wavelength specific decisions from the manufacturing process. For example, all line cards are manufactured the same, and the pluggable transceiver module with the desired wavelength (e.g. 850 nm, 1310 nm, 1550 nm, coarse wave division multiplexed (CWDM), dense wave division multiplexed (DWDM), etc.) is plugged in as a function of the specific application or development configuration. Network operators and service providers have adopted pluggable transceivers to reduce sparing costs. Further, significant cost reductions are realized by MSA standardization of pluggable transceivers because of multiple independent manufacturing sources.
The MSA specifications tightly define the mechanical characteristics, management interfaces, electrical characteristics, optical characteristics, and thermal requirements of pluggable transceivers. Advantageously, this enables interoperability among equipment vendors of pluggable transceivers, i.e. any MSA-compatible pluggable transceiver can be used in any host system designed to the MSA specification; however, these tightly defined characteristics limit the performance of pluggable transceivers since the MSA specifications were designed to maximize density and minimize cost, and not to provide advanced optical performance. To date, pluggable transceivers such as XFP, XPAK, XENPAK, X2, XFP-E, and SFP+ have been limited to short reach (less than 80 km) point-to-point applications without the need for high performance, extended reach, or advanced optical layer OAM&P. The MSA specifications have not addressed performance enhancements to enable pluggable transceivers to extend reach beyond 80 km and to provide carrier-grade optical management and performance. Where required to extend reach and to provide carrier-grade management and performance, host devices are designed with external circuitry interfaced to pluggable transceivers or pluggable transceivers are connected to optical transponders. As such, the use of pluggable transceivers to date has been limited to intra-office connections, short reach enterprise and metro networks (less than 80 km), and connection to an optical transponder capable of extended reach typically beyond 80 km.
Due to the low-cost, high-density, and widespread deployment of pluggable transceivers, both equipment vendors and network operators recognize a need to extend the benefits of pluggable transceivers to metro, regional and core network applications to enable carrier-grade wavelength division multiplexed (WDM) transport without the need for additional equipment such as optical transponders or additional circuitry performance enhancements. Such a need also must preserve the MSA mechanical characteristics, management interfaces, electrical characteristics, optical characteristics, and thermal requirements to maintain interoperability with existing host systems.